libc/test/src/stdio/ungetc_test.cpp

   1 //===-- Unittests for ungetc ----------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "src/stdio/ungetc.h"
  10
  11 #include "hdr/stdio_macros.h"
  12 #include "src/stdio/fclose.h"
  13 #include "src/stdio/fopen.h"
  14 #include "src/stdio/fread.h"
  15 #include "src/stdio/fseek.h"
  16 #include "src/stdio/fwrite.h"
  17 #include "test/UnitTest/Test.h"
  18
  19 TEST(LlvmLibcUngetcTest, UngetAndReadBack) {
  20   constexpr char FILENAME[] = "testdata/ungetc_test.test";
  21   ::FILE *file = LIBC_NAMESPACE::fopen(FILENAME, "w");
  22   ASSERT_FALSE(file == nullptr);
  23   constexpr char CONTENT[] = "abcdef";
  24   constexpr size_t CONTENT_SIZE = sizeof(CONTENT);
  25   ASSERT_EQ(CONTENT_SIZE,
  26             LIBC_NAMESPACE::fwrite(CONTENT, 1, CONTENT_SIZE, file));
  27 #ifndef LIBC_TARGET_ARCH_IS_GPU // Behavior varies between libc implementations.
  28   // Cannot unget to an un-readable file.
  29   ASSERT_EQ(EOF, LIBC_NAMESPACE::ungetc('1', file));
  30 #endif
  31   ASSERT_EQ(0, LIBC_NAMESPACE::fclose(file));
  32
  33   file = LIBC_NAMESPACE::fopen(FILENAME, "r+");
  34   ASSERT_FALSE(file == nullptr);
  35   // Calling with an EOF should always return EOF without doing anything.
  36   ASSERT_EQ(EOF, LIBC_NAMESPACE::ungetc(EOF, file));
  37   char c;
  38   ASSERT_EQ(LIBC_NAMESPACE::fread(&c, 1, 1, file), size_t(1));
  39   ASSERT_EQ(c, CONTENT[0]);
  40   ASSERT_EQ(LIBC_NAMESPACE::ungetc(int(c), file), int(c));
  41
  42   char data[CONTENT_SIZE];
  43   ASSERT_EQ(CONTENT_SIZE, LIBC_NAMESPACE::fread(data, 1, CONTENT_SIZE, file));
  44   ASSERT_STREQ(CONTENT, data);
  45
  46   ASSERT_EQ(0, LIBC_NAMESPACE::fseek(file, 0, SEEK_SET));
  47   // ungetc should not fail after a seek operation.
  48   int unget_char = 'z';
  49   ASSERT_EQ(unget_char, LIBC_NAMESPACE::ungetc(unget_char, file));
  50 #ifndef LIBC_TARGET_ARCH_IS_GPU // Behavior varies between libc implementations.
  51   // Another unget should fail.
  52   ASSERT_EQ(EOF, LIBC_NAMESPACE::ungetc(unget_char, file));
  53 #endif
  54   // ungetting a char at the beginning of the file will allow us to fetch
  55   // one additional character.
  56   char new_data[CONTENT_SIZE + 1];
  57   ASSERT_EQ(CONTENT_SIZE + 1,
  58             LIBC_NAMESPACE::fread(new_data, 1, CONTENT_SIZE + 1, file));
  59   ASSERT_STREQ("zabcdef", new_data);
  60
  61   ASSERT_EQ(size_t(1), LIBC_NAMESPACE::fwrite("x", 1, 1, file));
  62 #ifndef LIBC_TARGET_ARCH_IS_GPU // Behavior varies between libc implementations.
  63   // unget should fail after a write operation.
  64   ASSERT_EQ(EOF, LIBC_NAMESPACE::ungetc('1', file));
  65 #endif
  66
  67   ASSERT_EQ(0, LIBC_NAMESPACE::fclose(file));
  68 }